Backhaul is often spoken of as critical to telecom networks – but what is it? Which part of the mobile network is considered the “backhaul” network, and what does it do? We asked network experts to give us their backhaul network definitions.

Glen Hunt, principal analyst for transport and routing infrastructure at Current Analysis, gave his backhaul network definition as: “The backhaul network starts at the cell site, and ends up in the mobile core. So everything in between is what I’d consider the backhaul network.”

He went on to say, “you can segment that into the lower end of the backhaul network, which is closest to the cell site; and the upper end of the backhaul network, which could be aggregation sites and getting closer to the network controls and mobile core.

“If you can look at the backhaul network as, it’s an intermediary between the cell site and the intelligence in the network that can process the classes of traffic, and the data, and the video.”

“In my opinion, backhaul is actually the connections from the base station to the core network. It’s actually taking the traffic from the base station and backhauling it to the network,” said Eirik Nesse, vice president of strategy, backhaul provider Ceragon.

But, he added, a backhaul network definition is not set in stone.

“We also do transport networks – core network-based, connections with the core network. We still talk about it as backhaul, but it can be debated whether it is actually ‘transport’,” Nesse said. “Backhaul is a term that is not really well defined, but in general, about 70% of the market is base station connection, the links between the base stations and the core network.”

Ananth Nagarajan, senior director of product management at Juniper Networks, gave perspective on the history of cellular backhaul definitions and how the role of network intelligence within mobile backhaul has evolved.

“The traditional way of looking at backhaul is very transport-oriented,” he said. “You have signals from the cell tower or base station, and transport all of those signals back into a point in the network where you can apply intelligence – service provisioning, QoS. You apply that intelligence, then haul all that traffic back to the cell tower. There are a lot of inefficiencies; you’re simply using the backhaul for carrying all that traffic and not doing anything intelligent. That adds to the overall cost of the network, because you’re simply using a lot of infrastructure to carry traffic back and forth.”

As networks migrate to LTE, he added, the X2 interface allows new, smarter base stations to interact with one another via X2 traffic. Intelligence can be applied closer to the cell tower, instead of having all traffic routed to the network core because the necessary intelligence was limited to that location. User demand for excellent speed and connectivity is also expected to drive the deployment of small cells within LTE networks, with new backhaul challenges for these micro-sites that cannot simply be met by connecting wires, as with large macro sites.

According to a report by Ericsson (1), when it comes to Heterogeneous Networks with large deployments of small cells, “the level of integration between radio and backhaul equipment is likely to be much higher – perhaps with easily swappable backhaul interface units enabling radio units to be adapted, or upgraded, to the preferred backhaul option for the site. Scalability on a network level will be achieved only through the use of a well defined and carefully selected toolbox of backhaul technologies to manage both outdoor and indoor deployments on a large scale.”

Additional sources:

1. Ericsson white paper, It All Comes Back to Backhaul. http://www.ericsson.com/res/docs/whitepapers/WP-Heterogeneous-Networks-Backhaul.pdf